Enable crawler-friendly SSR/static pages for board content indexing

Description: As a community admin, I want board and topic pages to be served as crawlable, server-rendered/static HTML and to remove unintended crawler blocks, so that search engines and LLM crawlers can index our content reliably without executing JavaScript. Problem: Current board and topic pages rely heavily on client-side rendering and/or are blocked by robots directives, which prevents search engines and LLM crawlers from accessing and indexing the content. This limits discoverability, reduces organic traffic, and keeps our knowledge base hidden from AI assistants. Benefit: Improved SEO: Search engines can index thread lists and posts, increasing organic visibility. Better AI discoverability: LLM crawlers can learn from and surface our public content in answers. Faster share previews: Static/SSR pages provide better metadata for link unfurling. More consistent performance for crawlers and social bots, leading to more accurate indexing and previews.